Field of the Invention
The present invention relates to a sheet feeding apparatus which feeds a sheet stacked on a stacking member, and a reading apparatus and an image forming apparatus which are provided with the sheet feeding apparatus.
Description of the Related Art
In an original conveying and reading apparatus used in a copying machine and a facsimile apparatus, sheets (originals) stacked on a sheet stacking member are fed by a pickup roller (a feed rotating member), and separated one by one by a separation portion, and fed to a reading portion. Then, an image written in the sheet is optically read by the reading portion, and then the sheet is discharged to a discharge portion.
In a case where the pickup roller always abuts on the sheet stacked on the stacking member when the sheet is fed, there is a concern that a separating function of the separation portion may be degraded by a contact pressure between the pickup roller and the sheet when the fed sheet is separated by the separation portion. In addition, the contact pressure operates as a load when the fed sheet is drawn and conveyed by a pair of conveying rollers on the downstream side.
For this reason, the pickup roller is provided to be movable to a feed position where the pickup roller abuts on the sheet and to a retract position where the pickup roller is separated from the sheet stacked in a tray. When a leading edge of the sheet fed out by the pickup roller is detected by a sensor provided at a predetermined position, the pickup roller moves to the retract position. Then, the pickup roller comes to abut on the sheet again at a timing of feeding the next sheet to be fed out (Japanese Patent Laid-Open No. 2001-146329).
However, in the configuration of Patent Literature 1, the sensor may not always detect the leading edge of the sheet depending on the arrangement of the sensor to detect the leading edge of the sheet. For example, in a case where the sensor is disposed at the end portion in a sheet width direction (a direction orthogonal to a conveying direction), and when a sheet having a short width is fed, there is a concern that the sheet does not pass through a detection area of the sensor. Therefore, when the control is always performed only using the sensor, there is a concern that a defect occurs in the case of the sheet not passing through the detection area of the sensor.